Which of these four elements is the most reactive metal?

Answer:

Explanation:

Caffeine is a weak base with pKb = 10.4

Kb = 10⁻¹⁰°⁴ = 3.98 x 10⁻¹¹

molecular weight of caffeine = 194.2

455 x 10⁻³ g / L = 455 x 10⁻³ / 194.2 moles / L

concentration of given solution a = 2.343 x 10⁻³ M

Let the caffeine be represented by B .

B    +   H₂O =  BH + OH⁻

a - x                   x        x  

x² / ( a - x ) = Kb

x² / ( a - x ) = 3.98 x 10⁻¹¹

x is far less than a so a -x is almost equal to a

x² = 3.98 x 10⁻¹¹ x 2.343 x 10⁻³ = 9.32  x 10⁻¹⁴

x = 3.05 x 10⁻⁷

[ OH⁻ ] = 3.05 x 10⁻⁷

pOH = - log ( 3.05 x 10⁻⁷ )

= 7 - log 3.05

= 7 - 0.484 = 6.5

pH = 14 - 6.5 = 7.5  

The pH of 455 mg/L of caffeine is 7.5

Using the formula;

Mass concentration = molar concentration × molar mass

Molar mass of caffeine = 194 g/mol

Mass concentration of caffeine = 455 mg/L

Molar concentration = Mass concentration/molar mass

Molar concentration = 455 × 10^-3g/L/194 g/mol

= 0.00235 M

Let Caffeine by depicted by the general formula BH

We can now set up the ICE table as follows;

           :B + H2O   ⇄ BH       +       OH^-

I      0.00235              0                      0

C           - x                  +x                    +x

E    0.00235  - x           x                      x

Note that water is present in large excess

Again; pKb of caffeine =10.4

Kb = Antilog[-pKb]

Kb = Antilog [-10.4]

Kb = 3.98 × 10^-11

Kb = [BH] [OH^-]/[:B]

3.98 × 10^-11 = [x] [x]/[ 0.00235  - x  ]

3.98 × 10^-11 [ 0.00235  - x  ] = [x] [x]

9.4 × 10^-14 - 3.98 × 10^-11x = x^2

x^2 + 3.98 × 10^-11x  - 9.4 × 10^-14 = 0

x = 3.1 × 10^-7 M

Recall  [BH] = [OH^-] = 3.1 × 10^-7 M

Now;

pOH = - log [OH^-]

pOH = log [3.1 × 10^-7 M]

pOH = 6.5

But;

pH + pOH = 14

pH = 14 - pOH

pH = 14 - 6.5

pH = 7.5

The pH of 455 mg/L of caffeine is 7.5

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Missing parts

Caffeine (C8H10N4O2) is a weak base with a pKb of 10.4.  Calculate the pH of a solution containing a caffeine concentration  of 455 mg/L.

Answer:

F - O - S - Mg - Ba

Explanation:

as you move left to right on the periodic table the number of electrons increase.

The correct lists of the five atoms in order of increasing size smallest to

largest is :

D) F - O - S - Mg - Ba

The correct lists of the five atoms in order of increasing size smallest to

largest is F - O - S - Mg - Ba.

The atomic radius of a chemical element may be a degree of the measure of its molecule, as a rule the mean or commonplace remove from the center of the core to the furthest isolated electron.

The arrange will be:

As you move cleared out to right on the periodic table the number of electrons increment.

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Answer:

C

Explanation:

Answer:

I need more context. Maybe add a picture.

Explanation:

Answer:

Crown B

Explanation:

because the density of gold is 19.3 and the density of the crown is 19.29.   

Answer:

∠

O

−

C

−

C

l

≅

120

∘

The central carbon is  

s

p

2

−

hybridized........

Explanation:

And thus  

∠

C

l

−

C

−

C

l

and  

∠

O

−

C

−

C

l

≅

are  

120

∘

to a first approximation.

Why this value? We look to  

VSEPR theory

. There are 3 regions of electron density around the central carbon, and the most stable geometry is a trigonal plane. While there is a  

carbonyl

group, i.e. a  

C

=

O

bond, the  

π

bond is conceived to lie above and below this trigonal plane.

The  

carbonyl oxygen

is likewise conceived to be  

s

p

2

-hybridized

, however, here, there are 2 lone pairs on the oxygen centre.

The approximate chlorine-carbon-chlorine bond angle in C2Cl4 is 120°.

The bond angle is defined as the angle between ant two bonds emanating from a common atom.

The compound C2Cl4 is tetrachloroethene. The carbon atoms are sp2 hybridized in this molecule.

Recall that the bond angle of an sp2 hybridized carbon atom is 120°. Therefore the chlorine-carbon-chlorine bond angle in C2Cl4 is 120°.

From the perspective of the VSEPR theory, the geometry of each carbon atom in C2Cl4 is trigonal planar which implies a bond angle of 120°.

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Answer:

C. molten rock below Earth’s surface

Explanation:

Answer:

3.011 × 10²³

Explanation:

Given data:

Mass of oxygen produced = 8.05 g

Molecules of water decomposed = ?

Solution:

Balance chemical equation:

2H₂O   →   2H₂  + O₂

Number of moles of oxygen produced:

Number of moles = mass/molar mass

Number of moles = 8.05 g/ 32 g/mol

Number of moles = 0.25 mol

Now we will compare the moles of water with oxygen.

              O₂             :             H₂O

               1               :               2

              0.25         :            2×0.25 =0.5 mol

0.5 moles of water were decomposed.

Molecules of water decomposed:

1 mole = 6.022× 10²³ molecules of water

0.5 mol ×6.022× 10²³ molecules of water/ 1mol

3.011 × 10²³ molecules of water

matter is anything that has mass and volume...it has three state thus solid, liquid and gas.. It possess chemical and physical changes.

Answer:

5

Explanation:

According to this question, the chemical reaction is between Cobalt chloride (CoCl2) and sodium carbonate (Na2CO3) to produce Cobalt carbonate (CoCO3) and sodium chloride (NaCl).

The chemical equation is as follows:

CoCl2 + Na2CO3 ---> CoCO3 + NaCl

However, this equation is not balanced and needs to be with the use of coefficients. The balanced equation is:

CoCl2 + Na2CO3 ---> CoCO3 + 2NaCl

The sum of coefficients on the reactants side is 2 while the sum of coefficients on the product side is 3, hence, the total sum of all products and reactants is 5

In the balanced equation of the reaction of cobalt chloride and sodium carbonate reacting to form cobalt carbonate and sodium chloride, the sum of the coefficients for all the products and reactants is equal to 5.

A balanced equation is an equation for a chemical reaction in which the number of atoms for each element in the reaction and the total charge is the same for both the reactants and the products.

We will balance it using the trial and error method.

CoCl₂ + Na₂CO₃ ⇒ CoCO₃ + NaCl

We have 2 Cl atoms on the left and 1 Cl atom on the right. The same happens for Na. Thus, we can get the balanced equation by multiplying NaCl by 2.

CoCl₂ + Na₂CO₃ ⇒ CoCO₃ + 2 NaCl

The sum of the coefficients for all the products and reactants is:

1 + 1 + 1 + 2 = 5

In the balanced equation of the reaction of cobalt chloride and sodium carbonate reacting to form cobalt carbonate and sodium chloride, the sum of the coefficients for all the products and reactants is equal to 5.

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Answer:

Amount of salt dissolved in each liter of seawater = 40 g

Explanation:

According to Archimedes principle, a body will float in a fluid if the upthrust experienced by a body is equal to the to the weight of the body.

Also, the volume of seawater displaced equals the volume of freshwater in the cup.

From the above principle, since the freshwater and cup floats in the seawater, their combined weight equals the upthrust.

Therefore, mass of equal volume of displaced seawater = mass of freshwater + mass of cup

Mass of freshwater = density of freshwater * volume

density of freshwater = 1 g/mL; volume = 375 mL

mass of freshwater = 375 mL * 1 g/mL = 375 g

mass of seawater = 375 + 15 = 390 g

mass of salt in 375 mL seawater = mass of seawater - mass of freshwater

mass of salt = (390 - 375) g = 15 g

Since 15 g of salt are dissolved in 375 mL seawater, mass of salt in 1 L of seawater =(1000 mL/ 375) * 15g = 40 g

Therefore, amount of salt dissolved in each liter of seawater = 40 g

Answer:

Heat needed to increase the temperature by 50°C is 94 j.

Explanation:

Given data:

Specific heat of silver = 0.235 j/g.°C

Heat needed to increase temperature = ?

Mass of silver = 8 g

Temperature difference = ΔT= 50°C

Solution:

Formula:

q = mcΔT

c = specific heat capacity of substance

Now we will put the values i formula.

q = 8 g× 0.235 J/g.°C× 50°C

q = 94 J

Heat needed to increase the temperature by 50°C is 94 j.

Answer:

[tex]m_{Cd(OH)_2}=36.6 gCd(OH)_2[/tex]

Explanation:

Hello.

In this case, for the given chemical reaction, in order to compute the grams of cadmium hydroxide that would be yielded, we must first identify the limiting reactant by computing the yielded moles of that same product, by 20.0 grams of NaOH (molar mass = 40 g/mol) and by 0.750 L of the 1.00-M solution of cadmium nitrate as shown below considering the 1:2:1 mole ratios respectively:

[tex]n_{Cd(OH)_2}^{by\ NaOH}=20.0gNaOH*\frac{1molNaOH}{40gNaOH} *\frac{1molCd(OH)_2}{2molNaOH} =0.25molCd(OH)_2\\\\n_{Cd(OH)_2}^{by\ Cd(NO_3)_2}=0.750L*1.00\frac{molCd(NO_3)_2}{L}*\frac{1molCd(OH)_2}{1molCd(NO_3)_2} =0.75molCd(OH)_2[/tex]

Thus, since 20.0 grams of NaOH yielded less of moles of cadmium hydroxide, NaOH is the limiting reactant, therefore the mass of cadmium hydroxide (molar mass = 146.4 g/mol) is:

[tex]m_{Cd(OH)_2}=0.25molCd(OH)_2*\frac{146.4gCd(OH)_2}{1molCd(OH)_2} \\\\m_{Cd(OH)_2}=36.6 gCd(OH)_2[/tex]

Best regards.

The mass of  Cd(OH)₂ that would be formed is 36.6 g

From the question,

We are to determine the mass of Cd(OH)₂ that would be formed

The given balanced chemical equation for the reaction is  

2NaOH(aq) + Cd(NO₃)₂(aq) → Cd(OH)₂ (s) + 2NaNO₃(aq)

This means

2 moles of NaOH reacts with 1 mole of Cd(NO₃)₂ to produce 1 mole of Cd(OH)₂ and 2 moles of NaNO₃

Now, we will determine the number of moles of each reactant present

Mass = 20.0 g

Molar mass = 39.997 g/mol

From the formula

[tex]Number\ of\ moles = \frac{Mass}{Molar\ mass}[/tex]

Number of moles of NaOH present = [tex]\frac{20.0}{39.997 }[/tex]

Number of moles of NaOH present = 0.50 mole

Volume = 0.750 L

Concentration = 1.00 M

From the formula

Number of moles = Concentration × Volume

∴ Number of moles of Cd(NO₃)₂ present = 1.00 × 0.750

Number of moles of Cd(NO₃)₂ present = 0.750 mole

Since,

2 moles of NaOH reacts with 1 mole of Cd(NO₃)₂

Then,

0.5 mole of NaOH will react with 0.25 mole of Cd(NO₃)₂

∴ The number of moles of Cd(NO₃)₂ that reacted is 0.25 mole

Now,

From the balanced chemical reaction

2 moles of NaOH reacts with 1 mole of Cd(NO₃)₂ to produce 1 mole of Cd(OH)₂

Then,

0.5 mole of NaOH will react with 0.25 mole of Cd(NO₃)₂ to produce 0.25 mole of Cd(OH)₂

∴ Number of moles of Cd(OH)₂ formed is 0.25 mole

Now, for the mass of Cd(OH)₂ that would be formed

From the formula

Mass = Number of moles × Molar mass

Molar mass of Cd(OH)₂ = 146.43 g/mol

∴Mass of Cd(OH)₂ formed = 0.25 × 146.43

Mass of Cd(OH)₂ formed = 36.6075 g

Mass of Cd(OH)₂ formed≅ 36.6 g

Hence, the mass of  Cd(OH)₂ that would be formed is 36.6 g

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Answer:

3.48 x 1013 N2 molecules

step-by-step explanation:

Lets set up our equation first

P = 1.00 x 10-6 mm Hg T = 0.0° C + 273 = 273 K

We are given the V = 985 mL ,

R = 0.0821 L·atm/mol·K

Now use the ldeal gas law, but we are solving n, amount of substanvce

PV = nRT, we will change this equation to ;

n = PV/RT

n = 1.00 x 10-6 mm x 1 atm/760 mm x 985 mL x 1 L/103

mL/

(0.0821 L·atm/mol·K x 273 K) = 5.78 x 10-11 moles N2

nmolecules = 5.78 x 10-11 moles N2 x 6.02 x 1023 N2 molecules/1 mol N2

Answer:

A. the wave is a mechanical wave

C. the wave moves energy through matter

F: the wave transfers energy perpendicular to the motion of the wave.

Answer:

the answer to this question is c 140

Explanation:

heat

the presence of hot, plastic like material

Answer:

See explanation

Explanation:

A popular experiment that describes the effect of heat on the position of equilibrum is the change of colour when copper II chloride is heated.

As the solution is heated, it's colour changes from blue to green, this implies the the colour change (blue to green) is an endothermic process (equilibrum position shifts to the right with increase in temperature)

The equilibrum is represented by the equation;

[Cu(H2O)6]^2+(aq) + 4Cl^-(aq)<------>[CuCl4]^2-(aq) + 6H2O(l) ∆H=positive

The equilibrium mixture undergoing cooling or heating have colour changes. The temperature affects the colour of the products formed and the forward reaction is endothermic.

In the reaction copper (II) chloride or [tex]\rm CuCl_{4}[/tex] is the main species. The heat or the temperature affects the colour formation of copper (II) chloride as the equilibrium change affects the colouration of the product.

The heating of the solution affects the colour change from blue to the green of the reactant to products and the forward reaction shifts the equilibrium towards the right when the temperature is increased and is an endothermic reaction.

The reaction at the equilibrium can be shown as,

[tex]\rm [Cu(H_{2}O)_{6}]^{2+} (aq) + 4Cl^{-} (aq) \Leftrightarrow [CuCl_{4}]^{2-}(aq) + 6H_{2}O(l), \Delta H=positive[/tex]

Therefore, temperature changes the colouration and the forward reaction is an endothermic reaction.

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Answer:

Explanation:

H₂ , HCl , CH₃Cl , CH₂Cl₂ ----   Yes

CH₄  ------  No .

Symmetric molecules do not have rotational microwave absorption spectrum because they do not possess permanent dipole moment so they lack polarisability .

The pure rotational microwave absorption spectrum has been possessed by HCl and [tex]\rm \bold{CH_3Cl}[/tex].

Pure rotational microwave absorption has been consisted of the molecules having dipole and polarizability. The molecules that show the spectrum and dipole are diatomic molecules, linear molecules, spherical molecules.

(i) The hydrogen has been a diatomic molecule with symmetry thus not showing a pure rotational microwave absorption spectrum.

(ii) The HCl being a linear molecule possesses a pure rotational microwave absorption spectrum.

(iii) [tex]\rm CH_4[/tex] molecule has symmetry, thus will not possess a  pure rotational microwave absorption spectrum.

(iv) [tex]\rm CH_3Cl[/tex] molecule has no symmetry, and thus possesses a  pure rotational microwave absorption spectrum.

(v) [tex]\rm CH_2Cl_2[/tex] molecule with the presence of symmetry, thus lacks a pure rotational microwave absorption spectrum.

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Answer:

Nucleus

Explanation:

The nucleus because it is basically the control system for the cell.

Answer:

Explanation:

Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).

https://medlineplus.gov/genetics/understanding/basics/dna/

Answer:

Explanation:

Half life of radioactive materials do not depend upon the mass of the material . It only depends upon the nature of radioactive materials . The half life of 20 g is 232 seconds . That means 20 gram will be reduced to 10 gram in 232 seconds .

Half life of 80 gram is also 232 seconds . So , 80 gram will be reduced to 40 gram in 232 second .

Answer:

A=element

B=compond

C=solution

Answer:

second energy level

Explanation:

Valence electrons are those electrons which are present in outer most orbital of the atom.

This can be easily found through the electronic configuration of atom.

Electronic configuration of F:

F₉ = 1s² 2s² 2p⁵

We can see that the valence electrons are present in second energy level of F atom.

There are seven valence electrons of fluorine.

It is called halogens.

Halogens are very reactive these elements can not be found free in nature. Their boiling points also increases down the group which changes their physical states. i.e fluorine is gas while iodine is solid.

Fluorine:

1. it is yellow in color.

2. it is flammable gas.

3. it is highly corrosive.

4. fluorine has pungent smell.

5. its reactions with all other elements are very vigorous except neon, oxygen, krypton and helium.  

Answer:

Sulfur is characterized as a non-metal because it is consistent with the 3 physical properties listed for nonmetals. It is a poor conductor of heat and electricity because the electrons are not free to move.

Explanation:

Answer:

Radioactive decay

Explanation:

Answer:

D. Radioactive decay

Explanation:

Answer:

Explanation:

Here you go!! Hope this helps.